* ext/json/*, test/json/*: Update json-2.0.1.

Changes of 2.0.0: f679ebd0c6/CHANGES.md (2015-09-11-200)
  Changes of 2.0.1: f679ebd0c6/CHANGES.md (2016-07-01-201)
  [Feature #12542][ruby-dev:49706][fix GH-1395]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55576 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/json/test_helper.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: false
+case ENV['JSON']
+when 'pure'
+  $:.unshift 'lib'
+  require 'json/pure'
+when 'ext'
+  $:.unshift 'ext', 'lib'
+  require 'json/ext'
+else
+  $:.unshift 'ext', 'lib'
+  require 'json'
+end
+
+require 'test/unit'
+begin
+  require 'byebug'
+rescue LoadError
+end
+if ENV['START_SIMPLECOV'].to_i == 1
+  require 'simplecov'
+  SimpleCov.start
+end